Air conditioner and method of controlling the same

ABSTRACT

An air conditioner includes a compressor; a flow switching part disposed at an outlet side of the compressor to switch a flow direction of a refrigerant according to whether a cooling operation or heating operation is performed; an outdoor heat exchanger connected to the flow switching part and having a plurality of the refrigerant pipes to guide the refrigerant which heat-exchanges with outdoor air; and a main expansion valve connected to one side of the outdoor heat exchanger. A first inlet/outlet pipe connects the flow switching part to the outdoor heat exchanger; and a second inlet/outlet pipe connects the outdoor heat exchanger to the main expansion valve, where the outdoor heat exchanger includes a header to form a flowing space of the refrigerant and having an upper header and a lower header; a check valve disposed between the upper header and the lower header to guide the refrigerant to flow one way; and a bypass pipe connecting the lower header to the second inlet/outlet pipe and guiding a discharge of a liquid refrigerant located in the lower header, and a bypass pipe valve controlling an amount of the liquid refrigerant flowing through the bypass pipe.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §119 to KoreanApplication No. 10-2014-0147976, filed in Korea on Oct. 29, 2014, No.10-2014-0147977, filed in Korea on Oct. 29, 2014 and No.10-2014-0147978, filed in Korea on Oct. 29, 2014, whose entiredisclosure is hereby incorporated by reference.

BACKGROUND

1. Field

An air conditioner and a method of controlling the same are disclosedherein.

2. Background

An air conditioner is an apparatus which maintains air in a desiredspace at a desired temperature. Generally, the air conditioner includesa compressor, a condenser, an expander and an evaporator, and drives arefrigerant cycle by performing a compression process, a condensationprocess, an expansion process and an evaporation process of arefrigerant, and thus the desired space may be heated or cooled.

The desired space may be a space according to a place in which the airconditioner is used. For example, when the air conditioner is disposedat home or an office, the desired space may be an indoor space of ahouse or a building. When the air conditioner is disposed in a vehicle,the desired space may be a passenger compartment.

When the air conditioner performs a cooling operation, an outdoor heatexchanger provided at an outdoor unit serves as the condenser, and anindoor heat exchanger provided at an indoor unit serves as theevaporator. However, when the air conditioner performs a heatingoperation, the indoor heat exchanger serves as the condenser, and theoutdoor heat exchanger serves as the evaporator.

FIG. 1 is a view illustrating a structure of a conventional outdoor heatexchanger.

Referring to FIG. 1, the conventional outdoor heat exchanger 1 includesa plurality of refrigerant pipes 2 which are arranged in a plurality ofrows, a coupling plate 3 to which ends of the refrigerant pipes 2 arecoupled, and which supports the refrigerant pipes 2, and a header 4which branches the refrigerant into the refrigerant pipes 2 or combinesthe refrigerant passed through the refrigerant pipes 2.

The outdoor heat exchanger 1 further includes a return tube 7 whichchanges a flow direction of the refrigerant from one refrigerant pipe 2to another refrigerant pipe. For example, the return tube 7 may changethe flow direction of the refrigerant from one refrigerant pipe 2, whichis located in a first row of the refrigerant pipes 2 disposed in tworows, to another refrigerant pipe located in a second row.

The outdoor heat exchanger 1 further includes a plurality ofdistributors 5 and 6. The plurality of distributors 5 and 6 include afirst distributor 5 which branches and introduces the refrigerant intoat least a part of the refrigerant pipes among the plurality ofrefrigerant pipes 2, and a second distributor 6 which branches andintroduces the refrigerant into the rest of the plurality of refrigerantpipes 2.

In the outdoor heat exchanger 1 as described above, opposing flowdirections of the refrigerant are respectively formed in the heating andcooling operations.

For example, when the air conditioner performs the cooling operation,the outdoor heat exchanger 1 serves as the condenser (referring to asolid line arrow).

Specifically, the high pressure refrigerant compressed in the compressoris introduced into the header 4, branched into the plurality ofrefrigerant pipes 2, and heat-exchanged with outdoor air while flowingthrough the refrigerant pipes 2. The heat-exchanged refrigerant iscombined at the first and second distributors 5 and 6, and then flowstoward the indoor heat exchanger.

On the other hand, when the air conditioner performs the heatingoperation, the outdoor heat exchanger 1 serves as the evaporator(referring to a dotted line arrow).

Specifically, the refrigerant condensed in the indoor heat exchanger maybe depressurized while passing through the expander, and then may beintroduced into the outdoor heat exchanger 1. The refrigerant isbranched into the first and second distributors 5 and 6 at an entranceside of the outdoor heat exchanger 1, and then introduced into therefrigerant pipes 2 through a plurality of branch pipes connected toeach distributor.

At this time, the refrigerant is heat-exchanged with the outdoor airwhile flowing through the refrigerant pipes 2, and the heat-exchangedrefrigerant may be combined at the header 4 and then may flow toward thecompressor.

When the air conditioner performs the cooling operation, the refrigerantpassing through the outdoor heat exchanger 1 may be at a hightemperature and high pressure gaseous state. At this time, to increasecondensation efficiency of the refrigerant, it is advantageous to reducethe number of paths branched to the outdoor heat exchanger 1 and toincrease a length of each of the paths.

That is, by increasing a length of a flow path of the refrigerant, aflow speed of the refrigerant may be increased, and thus a condensingpressure of the refrigerant may be reduced. Therefore, the condensationefficiency, i.e., a phase change rate to a liquid state may be improved.

However, when the air conditioner performs the heating operation, therefrigerant passing through the outdoor heat exchanger 1 has two phases,a gaseous refrigerant and a liquid refrigerant. At this time, to reducea pressure loss of the refrigerant, it is advantageous to increase thenumber of the paths branched to the outdoor heat exchanger 1 and toreduce the length of each of the paths.

That is, a gaseous refrigerant of the two-phase refrigerant may have alarge pressure loss during flow. By reducing the length of the flow pathof the refrigerant and increasing the number of the paths, the pressureloss, i.e., an evaporating pressure drop may be prevented, and thusevaporation efficiency may be improved.

However, according to the structure of the conventional outdoor heatexchanger as illustrated in FIG. 1, when the air conditioner performsthe cooling operation and the heating operation, the number of the pathsthrough which the refrigerant is branched to the outdoor heat exchangerand the length of each of the paths are formed equally, and thus thereis a problem that the heat exchange efficiency is reduced.

That is, in the cooling operation, the condensing pressure in theoutdoor heat exchanger is increased, and thus the condensationefficiency is degraded. In the heating operation, the evaporatingpressure in the outdoor heat exchanger is reduced, and thus theevaporation efficiency is degraded.

SUMMARY

Therefore, the present disclosure is directed to an air conditionerhaving an outdoor heat exchanger in which heat exchange efficiency isimproved, and a method of controlling the same.

According to an aspect, there is provided an air conditioner including acompressor; a flow switching part disposed at an outlet side of thecompressor to switch a flow direction of a refrigerant according towhether a cooling operation or heating operation is performed; anoutdoor heat exchanger connected to the flow switching part and having aplurality of the refrigerant pipes to guide the refrigerant whichheat-exchanges with outdoor air; a main expansion valve connected to oneside of the outdoor heat exchanger; a first inlet/outlet pipe connectingthe flow switching part to the outdoor heat exchanger; and a secondinlet/outlet pipe connecting the outdoor heat exchanger to the mainexpansion valve, wherein the outdoor heat exchanger includes a header toform a flowing space of the refrigerant and having an upper header and alower header; a check valve disposed between the upper header and thelower header to guide the refrigerant to flow one way; and a bypass pipeconnecting the lower header to the second inlet/outlet pipe and to guidea discharge of a liquid refrigerant located in the lower header, and abypass pipe valve which controls an amount of the liquid refrigerantflowing through the bypass pipe.

The air conditioner may further include a detector disposed in therefrigerant flowing space of the header to detect the amount of theliquid refrigerant in the lower header.

The detector may include a liquid level sensor disposed in therefrigerant flowing space of the header to detect a level of the liquidrefrigerant introduced into the lower header.

The liquid level sensor may include a first liquid level sensor disposedat a lower side of the lower header such that a plurality of liquidlevel sensors are disposed above the first liquid level sensor.

The detector may include a temperature sensor disposed in therefrigerant flowing space of the header to detect a temperature of theliquid refrigerant introduced into the lower header.

The temperature sensor may include a first temperature sensor disposedat a lower side of the lower header such that a second temperaturesensor provided above the first temperature sensor.

When the amount of the liquid refrigerant measured by the detector ismore than a set range, the bypass pipe valve may be opened, and thus therefrigerant stored in the outdoor heat exchanger may be discharged fromthe outdoor heat exchanger, and when the amount of the liquidrefrigerant measured by the detector is less than the set range, thebypass pipe valve may be closed.

The outdoor heat exchanger may further include a first refrigerant pipeconnected to the upper header; a connection pipe to guide therefrigerant flowing through the first refrigerant pipe to the lowerheader; and a refrigerant introduction pipe connecting the lower headerto a second refrigerant pipe, and the refrigerant introduction pipe maybe higher than the connection pipe.

The refrigerant introduction pipe may include a lower introduction pipedisposed at a lower side of the lower header such that a plurality ofupper introduction pipes is disposed above the lowermost introductionpipe, and a height of the lower introduction pipe may be higher than aheight of the connection pipe with respect to a bottom of the outdoorheat exchanger.

The bypass pipe may extend from a surface of the lower header.

The bypass pipe valve may include an electronic expansion valve of adegree of opening is controllable.

The air conditioner may further include first and second distributionpipes branching from the second inlet/outlet pipe; and a first andsecond distributors connected to the respective first and seconddistribution pipes to branch and introduce the refrigerant into theplurality of refrigerant pipes.

The first distributor is connected to the first distribution pipe and incommunication with the upper header; and a second distributor isconnected to the second distribution pipe and in communication with thelower header.

The air conditioner may further include a first valve device disposed atthe first distribution pipe; and a second valve device disposed at thesecond distribution pipe.

The air conditioner may further include a third valve device disposed atthe connection pipe.

According to another aspect, there is provided method of controlling anair conditioner, including driving a cooling operation in an indoorunit; heat-exchanging a refrigerant to be discharged to the indoor unitthrough an outdoor heat exchanger, and introducing the refrigerant intothe outdoor heat exchanger; detecting an amount of a liquid refrigerantintroduced into the outdoor heat exchanger through a detector; andcontrolling a degree of opening of a valve disposed at a bypass pipe todischarge the liquid refrigerant from the outdoor heat exchanger, by acontroller based on the detected amount of the liquid refrigerant.

The controller controls by opening the bypass pipe valve when the amountof the liquid refrigerant detected by the detector is more than a setrange, and may close the bypass pipe valve, when the amount of theliquid refrigerant is less than the set range.

The detector may include a temperature sensor disposed at a refrigerantpath of the outdoor heat exchanger to detect a temperature of therefrigerant, and the amount of the liquid refrigerant introduced intothe outdoor heat exchanger may be detected through a temperature valueof the refrigerant detected by the temperature sensor.

The temperature sensor may include a first temperature sensor disposedat a lower side of the lower header; and a second temperature sensordisposed above the first temperature sensor.

The detector may include a liquid level sensor disposed at a refrigerantpath of the outdoor heat exchanger to detect a level of the liquidrefrigerant, and the amount of the liquid refrigerant introduced intothe outdoor heat exchanger may be detected through a level value of theliquid refrigerant detected by the liquid level sensor.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the followingdrawings in which like reference numerals refer to like elements, andwherein:

FIG. 1 is a view illustrating a conventional outdoor heat exchanger;

FIG. 2 is a view illustrating a structure of an air conditioneraccording to an embodiment of the present invention;

FIG. 3 is a view illustrating a main structure of an outdoor heatexchanger according to the embodiment of the present invention;

FIG. 4 is an enlarged view of a lower header of the outdoor heatexchanger according to the embodiment of the present invention;

FIG. 5 is a view illustrating a case in which a lowermost introductionpipe is formed lower than a height of a connection pipe;

FIG. 6 is an enlarged view of a lower head having a temperature sensoraccording to another embodiment of the present invention;

FIG. 7 is a block diagram of the air conditioner according to theembodiment of the present invention;

FIG. 8 is a flowchart of a method of controlling the outdoor heatexchanger according to a first embodiment of the present invention; and

FIG. 9 is a flowchart of a method of controlling the outdoor heatexchanger according to a second embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals may refer to like orcorresponding elements throughout the drawings and repeated descriptionthereof may be omitted. In addition, the components may be describedinterchangeably as “modules” and “parts” in this specification merelyfor the sake of convenience, and these terms do not have distinctmeanings or roles. Also, in the following description, if it isconsidered that the specific description of the related and well knownfunctions or structures may obscure the gist of the present invention,the specific description may be omitted. Also, the description proposedherein is just a preferable example for the purpose of illustrationonly, not intended to limit the scope of the invention, so it should beunderstood that other equivalents and modifications could be madethereto without departing from the spirit and scope of the invention.

FIG. 2 is a view illustrating a structure of an air conditioneraccording to an embodiment of the present invention, and FIG. 3 is aview illustrating a main structure of an outdoor heat exchangeraccording to the embodiment of the present invention.

Referring to FIG. 2, the air conditioner 10 according to the embodimentof the present invention includes an outdoor unit which is disposed atan outdoor area, and an indoor unit which is disposed at an indoor area.The indoor unit includes an indoor heat exchanger which heat-exchangeswith indoor air. FIG. 2 illustrates a structure of the outdoor unit.

The air conditioner 10 includes a plurality of compressors 110 and 112,and oil separators 120 and 122 which are disposed at outlet sides of theplurality of compressors 110 and 112 to separate oil from a refrigerantdischarged from the plurality of compressors 110 and 112.

The plurality of compressors 110 and 112 include a first compressor 110and a second compressor 112 which are connected in parallel with eachother. A discharge temperature sensor 114 which detects a temperature ofthe compressed refrigerant may be provided at each of the outlet sidesof the first and second compressors 110 and 112.

The oil separators 120 and 122 include a first oil separator 120 whichis disposed at the outlet side of the first compressor 110 and thesecond oil separator 122 which is disposed at the outlet side of thesecond compressor 112.

The air conditioner 10 includes a collection path 116, for collectingoil, from the oil separators 120 and 122 to the compressors 110 and 112.The collection path 116 extends from each of the outlet sides of thefirst and second oil separators 120 and 122 and then is combined, andthe combined path may be connected with pipes located at inlet sides ofthe first and second compressors 110 and 112.

A dryer 127 and a capillary 128 may be installed at the collection path116.

A high pressure sensor 125 which detects a high pressure of therefrigerant discharged from the compressors 110 and 112, and a flowswitching part 130 which guides the refrigerant passing through the highpressure sensor 125 toward an outdoor heat exchanger 200 or the indoorunit are provided at outlet sides of the oil separators 120 and 122. Forexample, the flow switching part 130 may include a four-way valve.

When the air conditioner performs a cooling operation, the refrigerantflows into the outdoor heat exchanger 200 from the flow switching part130. On the other hand, when the air conditioner performs a heatingoperation, the refrigerant flows from the flow switching part 130 towardan indoor heat exchanger of the indoor unit (not shown).

When air conditioner performs the cooling operation, the refrigerantcondensed in the outdoor heat exchanger 200 passes through a mainexpansion valve (an electronic expansion valve) 260. At this time, themain expansion valve 260 is completely opened, and thus does not performa decompression action on the refrigerant. That is, the main expansionvalve 260 may be installed at an outlet side of the outdoor heatexchanger 200 based on the cooling operation.

The refrigerant passing through the main expansion valve 260 passesthrough a heat sinking panel 265. The heat sinking panel 265 may beprovided at an electronic unit in which a heat generating component isprovided.

For example, the heat generating component may include a power module(an intelligent power module (IPM)). It may be understood that the IPMis a module in which a drive circuit and a protection circuit having aself-protecting function of a power device, such as MOSFET and IGBT, areinstalled.

The condensed refrigerant contacts the heat sinking panel 265, and coolsthe heat generating component.

The air conditioner 10 further includes a supercooling heat exchanger270 into which the refrigerant passing through the heat sinking panel265 is introduced, and a supercooling distributor 271 which is providedat an inlet side of the supercooling heat exchanger 270 to branch therefrigerant. The supercooling heat exchanger 270 serves as a middle heatexchanger which heat-exchanges with a first refrigerant circulating in asystem after some (a second refrigerant) of the first refrigerant isbranched.

Here, the first refrigerant is a refrigerant which is introduced intothe supercooling heat exchanger 270 via the supercooling distributor271, and may be supercooled by the second refrigerant. The secondrefrigerant may absorb heat from the first refrigerant.

The air conditioner 10 includes a supercooling path 273 which isprovided at an outlet side of the supercooling heat exchanger 270 toallow the second refrigerant to be branched from the first refrigerant.A supercooling expander 275 which depressurizes the second refrigerantis provided at the supercooling path 273. The supercooling expander 275may include an electronic expansion valve (EEV).

The second refrigerant in the supercooling path 273 may be introducedinto the supercooling heat exchanger 270, may heat-exchange with thefirst refrigerant, and then may flow to an inlet side of a gas-liquidseparator 280. The air conditioner 10 further includes a super-cooleddischarge temperature sensor 276 which detects a temperature of thesecond refrigerant passed through the supercooling heat exchanger 270.

The gas-liquid separator 280 is a device which separates and outputs agaseous refrigerant before the refrigerant is introduced into thecompressors 110 and 112. The separated gaseous refrigerant may beintroduced into the compressors 110 and 112.

While a refrigeration cycle is driven, the evaporated refrigerant may beintroduced into the gas-liquid separator 280 via the flow switching part130. At this time, the evaporated refrigerant is combined with thesecond refrigerant passing through the supercooling heat exchanger 270,and then introduced into the gas-liquid separator 280.

A suction temperature sensor 282 which detects a temperature of therefrigerant to be suctioned into the compressors 110 and 112 may beprovided at an inlet side of the gas-liquid separator 280.

Meanwhile, the first refrigerant passing through the supercooling heatexchanger 270 may be introduced into the indoor unit through an indoorunit connection pipe 279. The air conditioner 10 further includes aliquid line temperature sensor 278 which is provided at the outlet sideof the supercooling heat exchanger 270 to detect a temperature of thefirst refrigerant passed through the supercooling heat exchanger 270,i.e., a temperature of the supercooled refrigerant.

Hereinafter, the outdoor heat exchanger 200 and a peripheral structurethereof will be described.

The air conditioner 10 includes a first inlet/outlet pipe 201 a which isconnected from the flow switching part 130 to one side of the outdoorheat exchanger 200, and a second inlet/outlet pipe 201 b which isconnected from the other side of the outdoor heat exchanger 200 to themain expansion valve 260.

For example, the first inlet/outlet pipe 201 a may be connected to anupper portion of a header 205, i.e., an upper header 205 a, and thesecond inlet/outlet pipe 201 b may be connected to a lower portion ofthe header 205, i.e., a lower header 205 b.

When the air conditioner 10 performs the cooling operation, therefrigerant is introduced into the outdoor heat exchanger 200 throughthe first inlet/outlet pipe 201 a, and also discharged from the outdoorheat exchanger 200 through the second inlet/outlet pipe 201 b.

On the other hand, when the air conditioner 10 performs the heatingoperation, the refrigerant is introduced into the outdoor heat exchanger200 through the second inlet/outlet pipe 201 b, and discharged from theoutdoor heat exchanger 200 through the first inlet/outlet pipe 201 a.

The outdoor heat exchanger 200 includes a refrigerant pipe 202. Forexample, a plurality of refrigerant pipes 202 may be provided to formtwo rows in a horizontal direction and a plurality of columns in avertical direction. The plurality of refrigerant pipes 202 may bedisposed to be spaced apart from each other.

The plurality of refrigerant pipes 202 may be bent and then may extendlongitudinally. For example, in FIG. 3, the plurality of refrigerantpipes 202 may be formed to extend toward a rear of the figure and thento extend again toward a front thereof. In this case, the plurality ofrefrigerant pipes 202 may have a U shape.

The outdoor heat exchanger 200 further includes a coupling plate 203which supports the refrigerant pipes 202. The coupling plate 203includes a first plate 203 a which supports one side of the refrigerantpipes 202 having a bent shape, and a second plate 203 b which supportsthe other side thereof. The first and second plates 203 a and 203 bextend vertically.

The outdoor heat exchanger 200 further includes a return pipe 204 whichis coupled to ends of the plurality of refrigerant pipes 202 to guidethe refrigerant flowing in one refrigerant pipe 202 to anotherrefrigerant pipe 202. A plurality of return pipes 204 are provided, andcoupled to one side of the first and second plates 203 a and 203 b.

The outdoor heat exchanger 200 further includes the header 205 whichforms a flow space of the refrigerant. The header 205 may be configuredto branch and introduce the refrigerant into the plurality ofrefrigerant pipes 202 or to combine the refrigerant heat-exchanged atthe plurality of refrigerant pipes 202 according to whether the airconditioner 10 performs the cooling operation or the heating operation.The header 205 extends vertically corresponding to an extensiondirection of the first plate 203 a.

A plurality of refrigerant introduction pipes 232 extend between theheader 205 and the first plate 203 a. The plurality of refrigerantintroduction pipes 232 extend from the header 205, and are connected tothe refrigerant pipes 202 which are supported by the first plate 203 a.And the plurality of refrigerant introduction pipes 232 may be disposedto be vertically spaced apart from each other.

When the air conditioner 10 performs the cooling operation, therefrigerant in the header 205 may be introduced into the refrigerantpipes 202 through the plurality of refrigerant introduction pipes 232.On the other hand, when the air conditioner 10 performs the heatingoperation, the refrigerant in the refrigerant pipes 202 may beintroduced into the header 205 through the refrigerant introductionpipes 232.

The air conditioner 10 further includes a plurality of distributors 210and 220 which branch and introduce the refrigerant into the outdoor heatexchanger 200 based on the heating operation. The plurality ofdistributors 210 and 220 include a first distributor 210 and a seconddistributor 220.

The air conditioner 10 further includes a first distribution pipe 211and a second distribution pipe 221 which are branched from the secondinlet/outlet pipe 201 b to the respective first and second distributors210 and 220. The first distribution pipe 211 and the second distributionpipe 221 may extend from a branch part 201 c to the respective first andsecond distributors 210 and 220.

The air conditioner 10 further includes a first valve device 215 whichis installed at the first distribution pipe 211 to control an amount ofthe refrigerant flowing through the first distribution pipe 211, and asecond valve device 225 which is installed at the second distributionpipe 221 to control an amount of the refrigerant flowing through thesecond distribution pipe 221.

The first and second valve devices 215 and 225 may be an electronicexpansion valve of which an opening degree may be controlled.

The air conditioner 10 further includes a plurality of capillary tubes207 which extend from the first and second distributors 210 and 220 tothe plurality of refrigerant pipes 202. When the air conditioner 10performs the heating operation, the refrigerant is branched to the firstdistributor 210 and the second distributor 220, and flows to therefrigerant pipes 202 through the plurality of capillary tubes 207.

The air conditioner 10 further includes branch pipes 209 which connectthe plurality of capillary tubes 207 with the refrigerant pipes 202. Thebranch pipe 209 may branch the refrigerant flowing through the capillarytube 207 into two directions, i.e., toward one refrigerant pipe 202 andtoward another refrigerant pipe 202. For example, the branch pipe 209may be a Y-shaped branch pipe. A plurality of branch pipes 209 may beprovided corresponding to the number of the plurality of capillary tubes207.

When the air conditioner 10 performs the heating operation, therefrigerant introduced into the refrigerant pipes 202 through theplurality of capillary tubes 207 connected to the first distributor 210is heat-exchanged, and then introduced into the upper header 205 a ofthe header 205. The refrigerant introduced into the refrigerant pipes202 through the plurality of capillary tubes 207 connected to the seconddistributor 220 is heat-exchanged, and then introduced into the lowerheader 205 b of the header 205.

That is, the header 205 includes the upper header 205 a which is incommunication with the first distributor 210, and the lower header 205 bwhich is in communication with the second distributor 220. In FIG. 3, animaginary division line t1 which divides the upper header 205 a from thelower header 205 b is indicated.

The air conditioner 10 further includes a check valve 240 which isinstalled between the upper header 205 a and the lower header 205 b. Thecheck valve 240 allows a flow of the refrigerant from the lower header205 b to the upper header 205 a, and restricts the flow of therefrigerant from the upper header 205 a to the lower header 205 b.

Therefore, when the air conditioner 10 performs the heating operation,the refrigerant introduced into the refrigerant pipes 202 through thesecond distributor 220 may be heat-exchanged, may be introduced into thelower header 205 b, and may be guided to the upper header 205 a by thecheck valve 240. And the refrigerant introduced into the refrigerantpipes 202 through the first distributor 210 may be heat-exchanged, maybe introduced into the upper header 205 a, may be combined with therefrigerant introduced from the lower header 205 b, and may flow to thefirst inlet/outlet pipe 201 a.

The air conditioner 10 further includes a connection pipe 230 whichextends from one point of the first distribution pipe 211 to the lowerheader 205 b. A third valve device 235 which controls a flow rate of therefrigerant in the connection pipe 230 may be installed at theconnection pipe 230. For example, the third valve device 235 may includea solenoid valve which may be controlled to be switched on/off, or theelectronic expansion valve of which the opening degree is allowed.

When the air conditioner 10 performs the cooling operation, therefrigerant flowing from the first distributor 210 to the firstdistribution pipe 211 may be introduced into the lower header 205 bthrough the connection pipe 230.

The air conditioner 10 further includes a bypass pipe 250 which extendsfrom a lower end of the header 205, i.e., a lower end of the lowerheader 205 b to the second inlet/outlet pipe 201 b. When the airconditioner 10 performs the cooling operation, the bypass pipe 250 isformed to divert a liquid refrigerant accumulated at a lower portion ofthe header 205 to the second inlet/outlet pipe 201 b, i.e., the outletside of the outdoor heat exchanger 200.

Hereinafter, a flow of the refrigerant in the air conditioner 10 whilethe air conditioner 10 performs the heating operation and the coolingoperation will be described with reference to FIGS. 2 and 3.

First, when the air conditioner 10 performs the heating operation, oilis separated from the high temperature and high pressure refrigerantcompressed in the first and second compressors 110 and 112, while therefrigerant passes through the first and second oil separators 120 and122, and the separated oil is returned to the first and secondcompressors 110 and 112 through the collection path 116. And therefrigerant from which the oil is separated flows toward the indoor unitvia the flow switching part 130.

The refrigerant introduced into the indoor unit is condensed in theindoor heat exchanger, and the condensed refrigerant is introduced intothe supercooling heat exchanger 270 through the indoor unit connectionpipe 279. At this time, some of the refrigerant may be branched to thesupercooling path 273, may be depressurized in the supercooling expander275, and then may be introduced into the supercooling heat exchanger270.

Therefore, the condensed refrigerant and the refrigerant flowing throughthe supercooling path 273 heat-exchange with each other, and thus thecondensed refrigerant may be supercooled.

The supercooled refrigerant passed through the supercooling heatexchanger 270 may cool the heat generating component of the electronicunit, while passing through the heat sinking panel 265, and may bedepressurized in the main expansion valve 260.

The depressurized refrigerant may be branched from the branch part 201 cto the first and second distribution pipes 211 and 221, and then may beintroduced into the first and second distributors 210 and 220,respectively. At this time, the first and second valve devices 215 and225 may be opened by a predetermined opening degree. For example, thefirst and second valve devices 215 and 225 may be completely opened.

The refrigerant flowing to the first distributor 210 is introduced intothe refrigerant pipes 202 through the plurality of capillary tubes 207,heat-exchanged and then introduced into the upper header 205 a. Therefrigerant flowing to the second distributor 220 is introduced into therefrigerant pipes 202 through the plurality of capillary tubes 207,heat-exchanged and then introduced into the lower header 205 b. At thistime, the refrigerant may evaporate while being heat-exchanged.

The refrigerant introduced into the lower header 205 b flows to theupper header 205 a, and is combined with the refrigerant introduced intothe upper header 205 a. At this time, the refrigerant in the lowerheader 205 b may flow to the upper header 205 a via the check valve 240(referring to the dotted line arrow).

The combined refrigerant may be discharged to the first inlet/outletpipe 201 a connected to the upper header 205 a, and may be introducedinto the gas-liquid separator 280 via the flow switching part 130, andthe separated gaseous refrigerant may be suctioned into the first andsecond compressors 110 and 112. This cycle may be repeated.

Like this, when the air conditioner 10 performs the heating operation,the refrigerant may be introduced into the outdoor heat exchanger 200through the first and second distributors 210 and 220, and heat exchangemay be performed using all of a path at a side of the first distributor210 and a path at a side of the second distributor 220.

Therefore, the flow path of the refrigerant in the outdoor heatexchanger 200 is reduced, but the number of paths branched to theoutdoor heat exchanger 200 is increased. Accordingly, the pressure lossof the refrigerant may be reduced, and thus the evaporating pressuredrop may be prevented, and the evaporation efficiency may be improved.

When the air conditioner 10 performs the cooling operation, the oil isseparated from the high temperature and high pressure refrigerantcompressed in the first and second compressors 110 and 112, while therefrigerant passes through the first and second oil separators 120 and122, and the separated oil is returned to the first and secondcompressors 110 and 112 through the collection path 116. And therefrigerant from which the oil is separated flows toward the firstinlet/outlet pipe 201 a via the flow switching part 130, and isintroduced into the header 205 of the outdoor heat exchanger 200.

The refrigerant introduced into the header 205 is located at the upperheader 205 a, and restricted from being introduced into the lower header205 b by the check valve 240.

The refrigerant in the upper header 205 a is introduced into therefrigerant pipes 202 fixed to the first plate 203 a through theplurality of refrigerant introduction pipes 232. The refrigerant in therefrigerant pipes 202 is heat-exchanged, and then flows to the pluralityof capillary tubes 207 through the branch pipes 209. At this time, therefrigerant may be primarily condensed while being heat-exchanged.

The refrigerant in the plurality of capillary tubes 207 is combined inthe first distributor 210, and introduced into the lower header 205 bthrough the first distribution pipe 211 and the connection pipe 230. Atthis time, the first valve device 215 is closed, and thus therefrigerant is restricted from flowing to the branch part 201 c. And thethird valve device 235 is turned on, or opened by a predeterminedopening degree, and allows the refrigerant to flow to the connectionpipe 230.

The refrigerant introduced into the lower header 205 b is introducedinto the plurality of refrigerant pipes 202 fixed to the first plate 203a through the plurality of refrigerant introduction pipes 232. And therefrigerant may be secondarily condensed while flowing through theplurality of refrigerant pipes 202.

The secondarily condensed refrigerant is introduced into the seconddistributor 220 through the branch pipes 209 and the plurality ofcapillary tubes 207. The refrigerant in the second distributor 220 flowsthrough the second inlet/outlet pipe 201 b via the second distributionpipe 221 and the branch part 201 c, and is discharged from the outdoorheat exchanger 200.

The refrigerant discharged from the outdoor heat exchanger 200 may flowtoward the indoor unit via the heat sinking panel 265 and thesupercooling heat exchanger 270. The refrigerant may be expanded andevaporated in the indoor unit, and then may be suctioned into the firstand second compressors 110 and 120 via the flow switching part 130 andthe gas-liquid separator 280. This cycle may be repeated.

Like this, when the air conditioner 10 performs the cooling operation,the refrigerant introduced into the outdoor heat exchanger 200 isprimarily condensed in the refrigerant pipes 202 connected to a side ofthe upper header 205 a, and secondarily condensed in the refrigerantpipes 202 connected to a side of the lower header 205 b. Therefore, theflow path of the refrigerant in the outdoor heat exchanger 200 isincreased, but the number of paths branched to the outdoor heatexchanger 200 is reduced. Accordingly, the flow speed of the refrigerantis increased, and the condensing pressure is reduced, and thus thecondensation efficiency may be improved.

Meanwhile, the lower header 205 b may be filled with the liquidrefrigerant. Specifically, the refrigerant is primarily condensed whileflowing through the refrigerant pipes 202 connected to the upper header205 a, and thus may have two phases. Therefore, the refrigerantintroduced into the lower header 205 b through the connection pipe 230may be in a state in which a gas phase and a liquid phase are included.

Since the liquid refrigerant has a greater specific gravity than thegaseous refrigerant, the liquid refrigerant may fill a lower side of thelower header 205 b. It may be understood that the liquid refrigerant isa refrigerant which is completely condensed and which does not need theheat exchange any more. Therefore, when the liquid refrigerant isintroduced into the refrigerant pipes 202 and then heat-exchanged again,heat exchange performance of the heat exchanger may be degraded, and thepressure loss due to the liquid refrigerant may occur.

Therefore, the embodiment is characterized by providing the bypass pipe250 which diverts the liquid refrigerant to the outlet side of theoutdoor heat exchanger 200. The bypass pipe 250 extends from the lowerheader 205 b to the second inlet/outlet pipe 201 b, and discharges therefrigerant accumulated in the lower header 205 b to the secondinlet/outlet pipe 201 b during the cooling operation.

Hereinafter, a structure of the lower header 205 b will be described indetail with reference to FIG. 4.

FIG. 4 is an enlarged view of the lower header 205 b of the outdoor heatexchanger according to the embodiment of the present invention.

Referring to FIG. 4, the outdoor heat exchanger 200 according to theembodiment of the present invention includes the bypass pipe 250 whichdiverts the liquid refrigerant in the header 205 to the outlet side ofthe outdoor heat exchanger 200.

The bypass pipe 250 extends from a lower portion of the lower header 205b of the header 205 toward the second inlet/outlet pipe 201 b.

The outdoor heat exchanger 200 according to the embodiment of thepresent invention includes the plurality of refrigerant introductionpipes 232 which extend from the lower header 205 b to the plurality ofrefrigerant pipes 202. The plurality of refrigerant introduction pipes232 include a lowermost introduction pipe 232 a, and a plurality ofupper introduction pipes 232 b which are disposed above the lowermostintroduction pipe 232 a. A height H2 of the lowermost introduction pipe232 a may be formed higher than a height H1 of the connection pipe 230which extends from one point of the first distribution pipe 211 to thelower header 205 b. Here, it may be understood that each of the heightsH2 and H1 is a distance from a reference line t0, and, for example, thereference line t0 may be a base which forms a bottom of the outdoorunit, or a ground surface.

Like this, since the height H1 of the connection pipe 230 is formedlower than the height H2 of the lowermost introduction pipe 232 a, theliquid refrigerant in the lower header 205 b may be prevented from beingintroduced into the lowermost introduction pipe 232 a.

FIG. 5 is a view illustrating a case in which the lowermost introductionpipe is formed lower than the height of the connection pipe.

Hereinafter, an effect of the outdoor heat exchanger in which the heightof the connection pipe 230 is designed lower than the height of thelowermost introduction pipe 232 a will be described with reference toFIGS. 4 and 5.

As described above, the refrigerant introduced into the lower header 205b through the connection pipe 230 simultaneously contains the gas phaseand the liquid phase refrigerant. However, since the liquid refrigeranthas a greater specific gravity than the gaseous refrigerant, the liquidrefrigerant fills the lower side of the lower header 205 b, and thegaseous refrigerant fills above the liquid refrigerant. Therefore, apart of the plurality of refrigerant pipes which are in communicationwith the lower header 205 b are blocked by the liquid refrigerant.

As illustrated in FIG. 5, since the refrigerant introduction pipes 232disposed at an area A in which a liquid refrigerant L is located areblocked by the liquid refrigerant L, the gaseous refrigerant to besecondarily condensed may flow through only the refrigerant introductionpipes 232 disposed at an area B. Therefore, the gaseous refrigerant maynot smoothly flow to the plurality of refrigerant introduction pipes232, and thus the condensation efficiency and the heat exchangeperformance of the outdoor heat exchanger are degraded.

However, in the embodiment shown in FIG. 4, since the height H2 of thelowermost introduction pipe 232 a is formed higher than the height H1 ofthe connection pipe 230, the plurality of refrigerant introduction pipes232 are prevented from being blocked by the liquid refrigerant L, andthus the condensation efficiency and the heat exchange performance ofthe outdoor heat exchanger 200 may be improved.

Also, since the bypass pipe 250 is provided, the liquid refrigerant inthe lower header 205 b may be diverted to the outlet side of the outdoorheat exchanger 200, and thus the heat exchange performance of theoutdoor heat exchanger 200 may be improved.

In other words, since the liquid refrigerant filling the lower side ofthe lower header 205 b is a refrigerant which does not need to heatexchange, the liquid refrigerant may be diverted to the outlet side ofthe outdoor heat exchanger 200 through the bypass pipe 250, and thegaseous refrigerant which needs to heat exchange may be effectivelyheat-exchanged by the openings of all the plurality of refrigerantintroduction pipes 232.

And since the bypass pipe 250 extends downward from a lower surface ofthe lower header 205 b, the gaseous refrigerant in the lower header 205b may be prevented from being discharged through the bypass pipe 250 bya pressure difference between the gaseous refrigerant and the liquidrefrigerant.

Meanwhile, the air conditioner 10 further includes a bypass pipe valve252 which is installed at the bypass pipe 250 to control an amount ofthe refrigerant flowing through the bypass pipe 250.

The bypass pipe valve 252 may include an electronic expansion valve ofwhich an opening degree may be controlled.

When the bypass pipe valve 252 is opened, the liquid refrigerant fillingthe lower side of the lower header 205 b is diverted to the outlet sideof the outdoor heat exchanger 200, and when the bypass pipe valve 252 isclosed, the liquid refrigerant filling the lower side of the lowerheader 205 b is prevented from flowing to the outlet side of the outdoorheat exchanger 200.

As described above, the refrigerant introduced into the lower header 205b through the connection pipe 230 is in the state in which the gas phaseand the liquid phase are included. Therefore, since the liquidrefrigerant has the greater specific gravity than the gaseousrefrigerant, the liquid refrigerant may fill the lower side of the lowerheader 205 b. Since the liquid refrigerant is a refrigerant which iscompletely condensed and which does not need to heat exchange any more,the liquid refrigerant may be diverted to the outlet side of the outdoorheat exchanger 200 through the bypass pipe 250, and thus the heatexchange performance of the outdoor heat exchanger 200 may be enhanced.

Also, since a flow of the liquid refrigerant to the outlet side of theoutdoor heat exchanger 200 may be controlled by controlling the openingdegree of the bypass pipe valve 252, the liquid refrigerant may beprevented from accumulating at one side due to force of gravity, and thepressure loss of the refrigerant may be minimized, and thus efficiencyof the cooling operation may be maximized.

Meanwhile, a detector 30 (see, for example, FIG. 7) which detects theamount of the refrigerant may be provided at a refrigerant flowing spaceof the header 205. Specifically, the detector 30 is disposed at a pathin the lower header 205 b in which the primarily condensed refrigerantflows.

The detector 30 which detects an amount of the liquid refrigerant may beprovided at the lower header 205 b. Hereinafter, a method of detectingthe amount of the liquid refrigerant using the detector 30 will bedescribed.

FIG. 6 is an enlarged view of the lower head having a temperature sensoraccording to another embodiment of the present invention.

FIG. 4 illustrates the lower header 205 b in which a liquid level sensor290 is provided, and FIG. 6 illustrates the lower header 205 b in whicha temperature sensor 300 is provided. The liquid level sensor 290 andthe temperature sensor 300 are an example for detecting the amount ofthe liquid refrigerant introduced into the lower header 205 b. However,the present invention is not limited thereto, and various structures fordetecting the amount of the liquid refrigerant may be provided. Also,both of the liquid level sensor 290 and the temperature sensor 300 maybe disposed at the lower header 205 b.

Referring to FIG. 4, the detector 30 may include the liquid level sensor290 which is provided at an inside of the lower header 205 b to detect alevel of the liquid refrigerant introduced into the lower header 205 b.

Specifically, the liquid level sensor 290 may be provided at arefrigerant path of the lower header 205 b to be in contact with theliquid refrigerant, and thus to detect a liquid level in the lowerheader 205 b. That is, when the liquid level sensor 290 is in contactwith the liquid refrigerant, it indicates that the liquid refrigerant isintroduced into the lower header 205 b to a height at which the liquidlevel sensor is installed, and thus the amount of the liquid refrigerantmay be detected by calculating the height at which the liquid levelsensor is installed in the lower header 205 b.

For example, the liquid level sensor 290 may be disposed between thebypass pipe 250 and the connection pipe 230. Since the plurality ofrefrigerant introduction pipes 232 to which the refrigerant in the lowerheader 205 b flows so as to be secondarily condensed are blocked by anincrease in the amount of the liquid refrigerant, the gaseousrefrigerant which is required to be condensed may not be introduced intothe refrigerant pipes 202. Therefore, the liquid level sensor 290 isinstalled between the connection pipe 230 and the bypass pipe 250, andwhen the liquid refrigerant is at an amount that is detected by theliquid level sensor 290, the bypass pipe valve 252 may be opened, andthus the liquid refrigerant may be discharged to an outside of theoutdoor heat exchanger 200. Due to the discharge of the liquidrefrigerant, the gaseous refrigerant is introduced into the refrigerantpipes 202, and a secondary condensing process is performed.

Meanwhile, a plurality of liquid level sensors 290 may be disposed. Whenthe plurality of liquid level sensors 290 are provided, the liquid levelsensors 290 may include a first liquid level sensor 292 which isdisposed at the lowermost side of the lower header 205 b, and aplurality of liquid level sensors 293 which are disposed above the firstliquid level sensor 292. That is, the liquid level sensors 290 may beprovided at the inside of the lower header 205 b to be spaced upwardfrom each other at regular intervals from the lower surface of the lowerheader 205 b. In this case, there is an advantage that the amount of theliquid refrigerant introduced into the lower header 205 b may bedetected more specifically.

Referring to FIG. 6, the detector 30 may include the temperature sensor300 which is provided at the inside of the lower header 205 b to detecta temperature of the liquid refrigerant introduced into the lower header205 b.

The temperature sensor 300 may include a first temperature sensor 302which is installed adjacent to the lower surface of the lower header 205b, and a second temperature sensor 304 which is installed adjacent to anupper surface of the lower header 205 b.

Specifically, the first temperature sensor 302 is provided at the lowerportion of the lower header 205 b to be relatively close to the bypasspipe 250, and the second temperature sensor 304 is provided at the upperportion of the lower header 205 b to be relatively close to the checkvalve 240. Therefore, the first temperature sensor 302 may be referredto as a lower sensor 302, and the second temperature sensor 304 may bereferred to as an upper sensor 304.

The positions of the first and second temperature sensors 302 and 304are just an example, and may be variously installed to have differentinstallation heights in the lower header 205 b.

A method of detecting the amount of the liquid refrigerant introducedinto the lower header 205 b using the temperature sensor 300 will bedescribed.

When the bypass pipe valve 252 is closed, and thus the lower header 205b is filled from a lower end thereof with the liquid refrigerant, thefirst temperature sensor 302 adjacent to the lower end thereof detectsthe temperature of the liquid refrigerant. However, since the gaseousrefrigerant is located at the upper portion of the lower header 205 bwhich is not filled with the liquid refrigerant, and the gaseousrefrigerant has a relatively higher temperature than the liquidrefrigerant, the first temperature sensor 302 detects a relatively lowertemperature than the second temperature sensor 304.

When the liquid refrigerant is continuously introduced into the lowerheader 205 b, the liquid refrigerant fills the lower header 205 b to aninstallation height of the second temperature sensor 304. Therefore, thesecond temperature sensor 304 also detects the temperature of the liquidrefrigerant which is approximately similar to a value of the temperaturedetected by the first temperature sensor 302. Accordingly, it may bedetected that the liquid refrigerant fills the lower header 205 b to theinstallation height of the second temperature sensor 304.

Meanwhile, a plurality of temperature sensors 300 which are more thantwo may be provided. When more than two temperature sensors 300 areprovided, the temperature sensors 300 may be provided at the inside ofthe lower header 205 b to be spaced upward from each other at regularintervals from the lower surface of the lower header 205 b. In thiscase, there is an advantage that the amount of the liquid refrigerantintroduced into the lower header 205 b may be detected morespecifically.

Also, there is another advantage in that it is possible to grasp asupercooled degree of the liquid refrigerant and the gaseous refrigerantthrough the temperature sensor 300 and thus, determine a cooled state.

FIG. 7 is a block diagram of the air conditioner according to theembodiment of the present invention.

Referring to FIG. 7, the air conditioner 10 may include a controller 20,a detector 30, a memory 40 and a valve driver 50. Elements illustratedin FIG. 7 are not essential to realize the air conditioner, and thus theair conditioner 10 described in the specification may have more elementsor less elements than the above-described ones.

More specifically, the detector 30 among the elements is an elementwhich detects the amount of the refrigerant introduced into the lowerheader 205 b, as described above, and may include the liquid levelsensor 290 and/or the temperature sensor 300.

Various set values are inputted to the memory 40. For example, the setvalues may include an opening degree of the bypass pipe valve 252, aninstallation height of the liquid level sensor 290, a set range for adifference value of the temperature sensor 300 and so on.

The valve driver 50 receives a command from the controller based oninformation about the liquid refrigerant detected by the detector 30,and controls the opening degree of the bypass pipe valve 252.Specifically, the valve driver 50 includes a first valve driver 51 whichcontrols the opening degree of the first valve device 215, a secondvalve driver 52 which controls the opening degree of the second valvedevice 225, a third valve driver 53 which controls the opening degree ofthe third valve device 235, and a fourth valve driver 54 which controlsthe opening degree of the bypass pipe valve 252.

Typically, the controller 20 controls an overall operation of the airconditioner 10. The controller 20 serves to process a signal andinformation input or output through the above-described elements, or todrive the elements. The controller 20 may be a microprocessor, a digitalsignal processor (DSP), integrated circuit, or the like.

Hereinafter, a method of controlling the outdoor heat exchanger 200 willbe described using an example in which the air conditioner 10 performsthe cooling operation.

FIG. 8 is a flowchart of the method of controlling the outdoor heatexchanger according to a first embodiment of the present invention.

Referring to FIG. 8, the air conditioner 10 performs the coolingoperation (S100). The refrigerant introduced into the upper header 205 ais introduced into the lower header 205 b via the refrigerant pipe 202,the branch pipe 209, the first distributor 210 and the connection pipe230.

Therefore, in the lower header 205 b, there is the refrigerant havingthe two phases of the gaseous refrigerant and the liquid refrigerantwhich are mixed. However, since the liquid refrigerant has the greaterspecific gravity than the gaseous refrigerant, the liquid refrigerantfills the lower side of the lower header 205 b. At this time, the liquidlevel sensor 290 detects the liquid refrigerant filling the lower header205 b (S110).

And whether the level of the liquid refrigerant is increased to aninstallation height of the liquid level sensor 290 in the lower header205 b is detected (S120). When the level of the liquid refrigerant islower than the liquid level sensor 290, the bypass pipe valve 252 isclosed (S140), and thus the lower header 205 b is continuously filledwith the liquid refrigerant.

However, when the level of the liquid refrigerant is increased to theinstallation height of the liquid level sensor 290, the controller 20sends a signal to the valve driver 50, and thus the fourth valve driver54 opens the bypass pipe valve 252 (S130). Therefore, the liquidrefrigerant introduced into the lower header 205 b is diverted to theoutlet side of the outdoor heat exchanger 200 through the bypass pipe250, and thus the heat exchange performance in the outdoor heatexchanger 200 may be improved. Meanwhile, the gaseous refrigerantcontained in the introduced refrigerant is introduced into the pluralityof refrigerant introduction pipes 232, and then secondarily condensed.

FIG. 9 is a flowchart of a method of controlling the outdoor heatexchanger according to a second embodiment of the present invention.

Referring to FIG. 9, the air conditioner 10 performs the coolingoperation (S200). The refrigerant introduced into the upper header 205 ais introduced into the lower header 205 b via the refrigerant pipe 202,the branch pipe 209, the first distributor 210 and the connection pipe230.

The temperature sensor 300 detects the temperature of the introducedrefrigerant (S210).

The plurality of temperature sensors 300 are provided to have heightsdifferent from each other. Since the gaseous refrigerant contained inthe refrigerant having the two phases has a different temperature fromthe liquid refrigerant, and the lower side of the lower header 205 b isfilled with the liquid refrigerant, a temperature detected at the lowersurface of the lower header 205 b is lower at the beginning.

That is, the first temperature sensor 302 among the plurality oftemperature sensors is disposed at the lower side of the lower header205 b first detects the temperature of the liquid refrigerant. Thesecond temperature sensor 304 is disposed at the upper side of the lowerheader 205 b. When the lower header 205 b is filled with the liquidrefrigerant to the installation height of the second temperature sensor304, the second temperature sensor 304 detects the temperature of theliquid refrigerant.

In other words, in the beginning, the temperature detected by the firsttemperature sensor 302 which detects the temperature of the liquidrefrigerant is lower than that detected by the second temperature sensor304 which detects the temperature of the gaseous refrigerant. When theliquid refrigerant fills continuously, and thus the second temperaturesensor 304 detects the temperature of the liquid refrigerant, the firstand second temperature sensors 302 and 304 have the similar temperaturevalues.

The controller 20 compares the first temperature sensor 302 with thesecond temperature sensor 304 (S220). When a difference between thetemperature values detected by the first and second temperature sensors302 and 304 deviates from a set range in the memory 40, it indicatesthat the liquid refrigerant has not filled to the installation height ofthe second temperature sensor 304, and thus the controller 20 controlsthe valve driver 50 so that the fourth valve driver 54 has the bypasspipe valve 252 closed (S240). When the bypass pipe valve 252 is closed,the lower header 205 b is continuously filled with the liquidrefrigerant.

However, when the difference between the temperature values detected bythe first and second temperature sensors 302 and 304 is within the setrange, it indicates that the liquid refrigerant has filled to theinstallation height of the second temperature sensor 304, and thus thecontroller 20 sends a command to the valve driver 50 to open the bypasspipe valve 252 (S230). Therefore, the liquid refrigerant introduced intothe lower header 205 b is diverted to the outlet side of the outdoorheat exchanger 200 through the bypass pipe 250, and thus the heatexchange performance of the outdoor heat exchanger 200 may be improved.

The air conditioner and the method of controlling the same have thefollowing effects.

During the cooling operation and the heating operation of the airconditioner, the number of the paths through which the refrigerantpasses through the outdoor heat exchanger and the length of each of thepaths are formed differently, and thus the heat exchange efficiency inthe outdoor heat exchanger can be improved.

Specifically, when the air conditioner performs the heating operation,the number of the paths through which the refrigerant is introduced intothe outdoor heat exchanger can be reduced, and the length of each of thepaths can be increased. Therefore, the flow speed of the refrigerant isincreased, and the condensing pressure is reduced, and thus thecondensation efficiency can be improved.

Also, since there is provided the bypass pipe through which the liquidrefrigerant in the lower side of the header of the outdoor heatexchanger is diverted to the outlet side of the outdoor heat exchanger,the liquid refrigerant can be prevented from accumulating at the lowerside of the header during the cooling operation.

Eventually, since the liquid refrigerant which is already condensed, andthus does not need to heat exchange can be discharged from the outdoorheat exchanger, the heat exchange performance (the condensationperformance) of the outdoor heat exchanger can be improved, and thepressure loss due to the liquid refrigerant can be prevented.

Also, there is an advantage that it is possible to detect the state ofthe amount of the liquid refrigerant and the gaseous refrigerant throughthe detecting sensor provided at the lower header.

Also, there is another advantage that the cooling efficiency and theheat exchange efficiency of the heat exchanger can be enhanced bycontrolling the opening degree of the valve provided at the bypass pipeaccording to detected information.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. An air conditioner comprising: a compressor; aflow switching part disposed at an outlet side of the compressor toswitch a flow direction of a refrigerant according to whether a coolingoperation or heating operation is performed; an outdoor heat exchangerconnected to the flow switching part and having a plurality of therefrigerant pipes to guide the refrigerant which heat-exchanges withoutdoor air; a main expansion valve connected to one side of the outdoorheat exchanger; a first inlet/outlet pipe connecting the flow switchingpart to the outdoor heat exchanger; and a second inlet/outlet pipeconnecting the outdoor heat exchanger to the main expansion valve,wherein the outdoor heat exchanger comprises: a header to form a flowingspace of the refrigerant and including an upper header and a lowerheader; a check valve disposed between the upper header and the lowerheader to guide the refrigerant to flow one way; a bypass pipeconnecting the lower header to the second inlet/outlet pipe and to guidea discharge of a liquid refrigerant located in the lower header; and abypass pipe valve that is installed on the bypass pipe and controls anamount of the liquid refrigerant flowing through the bypass pipe.
 2. Theair conditioner according to claim 1, further comprising a detectordisposed in the refrigerant flowing space of the header to detect theamount of the liquid refrigerant in the lower header.
 3. The airconditioner according to claim 2, wherein the detector comprises aliquid level sensor disposed in the refrigerant flowing space of theheader to detect a level of the liquid refrigerant introduced into thelower header.
 4. The air conditioner according to claim 3, wherein theliquid level sensor comprises a first liquid level sensor disposed at alower side of the lower header such that a plurality of liquid levelsensors are disposed above the first liquid level sensor.
 5. The airconditioner according to claim 2, wherein the detector comprises atemperature sensor disposed in the refrigerant flowing space of theheader to detect a temperature of the liquid refrigerant introduced intothe lower header.
 6. The air conditioner according to claim 5, whereinthe temperature sensor comprises a first temperature sensor disposed ata lower side of the lower header such that a second temperature sensoris disposed above the first temperature sensor.
 7. The air conditioneraccording to claim 2, wherein, when the amount of the liquid refrigerantmeasured by the detector is more than a set range, the bypass pipe valveis opened, and the liquid refrigerant stored in the outdoor heatexchanger is discharged from the outdoor heat exchanger, and when theamount of the liquid refrigerant measured by the detector is less thanthe set range, the bypass pipe valve is closed.
 8. The air conditioneraccording to claim 1, wherein the outdoor heat exchanger furthercomprises a first refrigerant pipe connected to the upper header; aconnection pipe to guide the refrigerant flowing through the firstrefrigerant pipe to the lower header; and a refrigerant introductionpipe connecting the lower header to a second refrigerant pipe, and therefrigerant introduction pipe located higher than the connection pipe.9. The air conditioner according to claim 8, wherein the refrigerantintroduction pipe comprises a lower introduction pipe disposed at alower side of the lower header such that a plurality of upperintroduction pipes is disposed above the lower introduction pipe, and aheight of the lower introduction pipe is higher than a height of theconnection pipe with respect to a bottom of the outdoor heat exchanger.10. The air conditioner according to claim 1, wherein the bypass pipeextends from a surface of the lower header.
 11. The air conditioneraccording to claim 1, wherein the bypass pipe valve comprises anelectronic expansion valve of which a degree of opening is controllable.12. The air conditioner according to claim 1, further comprising: firstand second distribution pipes branching from the second inlet/outletpipe; and a first and second distributors connected to the respectivefirst and second distribution pipes to branch and introduce therefrigerant into the plurality of refrigerant pipes.
 13. The airconditioner according to claim 12, wherein the first distributor isconnected to the first distribution pipe and in communication with theupper header; and the second distributor is connected to the seconddistribution pipe and in communication with the lower header.
 14. Theair conditioner according to claim 12, further comprising: a first valvedevice disposed at the first distribution pipe; and a second valvedevice disposed at the second distribution pipe.
 15. The air conditioneraccording to claim 8, further comprising a third valve device disposedat the connection pipe.
 16. A method of controlling an air conditioner,comprising: driving a cooling operation in an indoor unit to allowrefrigerant discharged from a compressor to be introduced into theoutdoor heat exchanger; detecting an amount of a liquid refrigerantintroduced into the outdoor heat exchanger by a detector; andcontrolling a degree of opening of a valve disposed at a bypass pipe todischarge the liquid refrigerant from the outdoor heat exchanger, by acontroller based on the detected amount of the liquid refrigerant. 17.The method according to claim 16, wherein the controller controls byopening the bypass pipe valve when the amount of the liquid refrigerantdetected by the detector is more than a set range, and closes the bypasspipe valve when the amount of the liquid refrigerant is less than theset range.
 18. The method according to claim 16, wherein the detectorcomprises a temperature sensor disposed at a refrigerant path of theoutdoor heat exchanger to detect a temperature of the refrigerant, andthe controller determines the amount of the liquid refrigerantintroduced into the outdoor heat exchanger based on a temperature valueof the refrigerant detected by the temperature sensor.
 19. The methodaccording to claim 18, wherein the temperature sensor comprises: a firsttemperature sensor disposed at a lower side of the lower header; and asecond temperature sensor disposed above the first temperature sensor.20. The method according to claim 16, wherein the detector comprises aliquid level sensor disposed at a refrigerant path of the outdoor heatexchanger to detect a level of the liquid refrigerant, and thecontroller determines the amount of the liquid refrigerant introducedinto the outdoor heat exchanger based on a level value of the liquidrefrigerant detected by the liquid level sensor.